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Three-two pull down (3:2 pull down) is a term used in filmmaking and television production for the post-production process of transferring film to video.
It converts 24 frames per second into 29.97 frames per second, converting approximately every 4 frames into 5 frames plus a slight slow down in speed. Film runs at a standard rate of 24 frames per second, whereas NTSC video has a signal frame rate of 29.97 frames per second. Every interlaced video frame has two fields for each frame. The three-two pull down is where the telecine adds a third video field (a half frame) to every second video frame, but the untrained eye cannot see the addition of this extra video field. In the figure, the film frames A–D are true or original images since they have been photographed as a complete frame. The A, B, and D frames on the right in the NTSC footage are original frames. The third and fourth frames have been created by blending movie fields from different frames.
In the United States and other countries where television uses the 59.94 Hz vertical scanning frequency, video is broadcast at 29.97 frame/s. For the film's motion to be accurately rendered on the video signal, a telecine must use a technique called the 2:3 pull down (or a variant called 3:2 pull down) to convert from 24 to 29.97 frame/s.
The term “pulldown” comes from the mechanical process of “pulling” (physically moving) the film downward within the film portion of the transport mechanism, to advance it from one frame to the next at a repetitive rate (nominally 24 frames/s). This is accomplished in two steps.
The first step is to slow down the film motion by 1/1000 to 23.976 frames/s (or 24 frames every 1.001 seconds). The difference in speed is imperceptible to the viewer. For a two-hour film, play time is extended by 7.2 seconds.
The second step of the 2:3 pulldown is distributing cinema frames into video fields. At 23.976 frame/s, there are four frames of film for every five frames of 29.97 Hz video:
These four frames needs to be “stretched” into five frames by exploiting the interlaced nature of video. Since an interlaced video frame is made up of two incomplete fields (one for the odd-numbered lines of the image, and one for the even-numbered lines), conceptually four frames need to be used in ten fields (to produce five frames).
The term "2:3" comes from the pattern for producing fields in the new video frames. The pattern of 2-3 is an abbreviation of the actual pattern of 2-3-2-3, which indicates that the first film frame is used in 2 fields, the second film frame is used in 3 fields, the third film frame is used in 2 fields, and the fourth film frame is used in 3 fields—producing a total of 10 fields, or 5 video frames. If the four film frames are called A, B, C and D, the five video frames produced are A1-A2, B1-B2, B2-C1, C2-D1 and D1-D2. That is, frame A is used 2 times (in both fields of the first video frame); frame B is used 3 times (in both fields of the second video frame and in one of the fields of the third video frame); frame C is used 2 times (in the other field of the third video frame, and in one of the fields of the fourth video frame); and frame D is used 3 times (in the other field of the fourth video frame, and in both fields of the fifth video frame). The 2-3-2-3 cycle repeats itself completely after four film frames have been exposed.
The alternative "3:2" pattern is similar to the one shown above, except it is shifted by one frame. For instance, a cycle that starts with film frame B yields a 3:2 pattern: B1-B2, B2-C1, C2-D1, D1-D2, A1-A2 or 3-2-3-2 or simply 3-2. In other words, there is no difference between the 2-3 and 3-2 patterns. In fact, the "3-2" notation is misleading because according to SMPTE standards for every four-frame film sequence the first frame is scanned twice, not three times.
The above method is a "classic" 2:3, which was used before frame buffers allowed for holding more than one frame. It has the disadvantage of creating two dirty frames (which are a mix from two different film frames) and three clean frames (which matches an unmodified film frame) in every five video frames.
The preferred method for doing a 2:3 creates only one dirty frame in every five (i.e. 3:3:2:2 or 2:3:3:2 or 2:2:3:3). The 3-3-2-2 pattern produces A1-A2 A2-B1 B1-B2 C1-C2 D1-D2, where only the second frame is dirty. While this method has a slight bit more judder, it allows for easier upconversion (the dirty frame can be dropped without losing information) and a better overall compression when encoding. The 2:3:3:2 pattern is supported by the Panasonic DVX-100B video camera under the name "Advanced Pulldown". Note that just fields are displayed—no frames hence no dirty frames—in interlaced displays such as on a CRT. Dirty frames may appear in other methods of displaying the interlaced video.
The rate of NTSC video (initially monochrome, only, but soon thereafter monochrome and color) is 29.97 frames per second, or one-thousandth slower than 30 frame/s, due to the NTSC color encoding process which mandated that the line rate be a sub-multiple of the 3.579545 MHz color "burst" frequency, or 15734.2637 Hz (29.9700 Hz, frame rate), rather than the (60 Hz) ac "line locked" line rate of 15750.0000… Hz (30.0000… Hz, frame rate). This seemingly odd relationship proved to be essential to eliminating moiré and other image defects.
Although slight, the sync will catch up, and the audio can end up being several seconds out of sync with the image. In order to correct this error, the telecine can either pull up or pull down. A pull up will speed up the sound by 0.1%, used for transferring video to film. A pull down will slow the audio speed down by 0.1%, necessary for transferring film to video.
MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard.
The abbreviation NTSC can refer to the National Television System Committee, which developed the analog television color system that was introduced in North America in 1954 and stayed in use until digital conversion. NTSC is also an abbreviation for the National Television Standards Committee, a subset of the National Television System Committee that was responsible for producing the detailed technical specifications for the transmission standard. It is one of three major analog color television standards, the others being PAL and SECAM.
Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon.
Telecine is the process of transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process. Telecine enables a motion picture, captured originally on film stock, to be viewed with standard video equipment, such as television sets, video cassette recorders (VCR), DVD, Blu-ray Disc or computers. Initially, this allowed television broadcasters to produce programmes using film, usually 16mm stock, but transmit them in the same format, and quality, as other forms of television production. Furthermore, telecine allows film producers, television producers and film distributors working in the film industry to release their products on video and allows producers to use video production equipment to complete their filmmaking projects. Within the film industry, it is also referred to as a TK, because TC is already used to designate timecode. Motion picture film scanners are similar to telecines.
A line doubler is a device or algorithm used to deinterlace video signals prior to display on a progressive scan display.
Broadcast television systems are the encoding or formatting standards for the transmission and reception of terrestrial television signals. There were three main analog television systems in use around the world until the late 2010s (expected): NTSC, PAL, and SECAM. Now in digital terrestrial television (DTT), there are four main systems in use around the world: ATSC, DVB, ISDB and DTMB.
The refresh rate is the number of times per second that a raster-based display device displays a new image. This is independent from frame rate, which describes how many images are stored or generated every second by the device driving the display.
In video technology, 24p refers to a video format that operates at 24 frames per second frame rate with progressive scanning. Originally, 24p was used in the non-linear editing of film-originated material. Today, 24p formats are being increasingly used for aesthetic reasons in image acquisition, delivering film-like motion characteristics. Some vendors advertise 24p products as a cheaper alternative to film acquisition.
Deinterlacing is the process of converting interlaced video into a non-interlaced or progressive form. Interlaced video signals are commonly found in analog television, digital television (HDTV) when in the 1080i format, some DVD titles, and a smaller number of Blu-ray discs.
720p is a progressive HDTV signal format with 720 horizontal lines and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcasting standards include a 720p format, which has a resolution of 1280×720; however, there are other formats, including HDV Playback and AVCHD for camcorders, that use 720p images with the standard HDTV resolution. The frame rate is standards-dependent, and for conventional broadcasting appears in 50 progressive frames per second in former PAL/SECAM countries, and 59.94 frames per second in former NTSC countries.
480i is the video mode used for standard-definition analog or digital television in the Caribbean, Myanmar, Japan, South Korea, Taiwan, Philippines, Laos, Western Sahara, and most of the Americas. The 480 identifies a vertical resolution of 480 lines, and the i identifies it as an interlaced resolution. The field rate, which is 60 Hz, is sometimes included when identifying the video mode, i.e. 480i60; another notation, endorsed by both the International Telecommunication Union in BT.601 and SMPTE in SMPTE 259M, includes the frame rate, as in 480i/30. The other common standard, used in the other parts of the world, is 576i.
576i is a standard-definition video mode originally used for terrestrial television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with the colour encoding system, it is often referred to as simply PAL, PAL/SECAM or SECAM when compared to its 60 Hz NTSC-colour-encoded counterpart, 480i. In digital applications it is usually referred to as "576i"; in analogue contexts it is often called "625 lines", and the aspect ratio is usually 4:3 in analogue transmission and 16:9 in digital transmission.
Film-out is the process in the computer graphics, video production and filmmaking disciplines of transferring images or animation from videotape or digital files to a traditional film print. "Film-out" is a broad term that encompasses the conversion of frame rates, color correction, as well as the actual printing, also called scannior recording.
Progressive segmented Frame is a scheme designed to acquire, store, modify, and distribute progressive scan video using interlaced equipment.
Cinema Tools is a software program for filmmakers, to use in conjunction with Final Cut Pro. It facilitates the creation of an integrated film database, allowing the management of film material through telecine.
This article discusses moving image capture, transmission and presentation from today's technical and creative points of view; concentrating on aspects of frame rates.
Television standards conversion is the process of changing a television transmission or recording from one television system to another. The most common is from NTSC to PAL or the other way around. This is done so television programs in one nation may be viewed in a nation with a different standard. The video is fed through a video standards converter, which makes a copy in a different video system.
Rec. 709, also known as Rec.709, BT.709, and ITU 709, is a standard developed by ITU-R for image encoding and signal characteristics of high-definition television.
High-definition television (HD) describes a television system providing an image resolution of substantially higher resolution than the previous generation of technologies. The term has been used since 1936, but in modern times refers to the generation following standard-definition television (SDTV), often abbreviated to HDTV or HD-TV. It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television, and Blu-ray Discs.